🧪 Performance Testing with K6: A Complete Guide with Examples Link to heading

📌 Introduction Link to heading

When building modern web applications, ensuring they can handle a high load of users is essential. K6 is a developer-centric open-source load testing tool built for making performance testing simple, efficient, and fun.

K6 enables developers and QA engineers to write load tests using JavaScript, execute them locally or in the cloud, and gain insights into performance bottlenecks before they impact real users.

🚀 Why Use K6? Link to heading

• 📜 Written in JavaScript
• 🧪 Load, stress, and soak testing
• 🧰 CLI-based tool, easy to integrate in CI/CD pipelines
• 📊 Rich output for metrics
• ☁️ Cloud execution with k6 Cloud

🔍 How K6 Differs from Other Tools Link to heading

K6 offers a unique approach to performance testing compared to traditional tools like JMeter, Gatling, or Locust. Here’s a breakdown:

Summary:

• K6 is ideal for developers who prefer coding tests directly.
• JMeter is better suited for testers who prefer a GUI.
• Gatling and Locust are also code-based but require Scala or Python, respectively.

K6 is especially strong for:

• Modern DevOps practices
• Script versioning in Git
• Integrations with Grafana for dashboards

🛠️ Installation Link to heading

Install using Homebrew (macOS):

brew install k6

Or using Chocolatey (Windows):

choco install k6

Or via Docker:

docker run -i loadimpact/k6 run - <script.js

📄 Basic Example Link to heading

Simple Load Test Script (script.js) Link to heading

import http from 'k6/http';
import { sleep } from 'k6';

export const options = {
  vus: 10, // virtual users
  duration: '30s', // test duration
};

export default function () {
  http.get('https://test.k6.io');
  sleep(1);
}

Run the test Link to heading

k6 run script.js

📦 Project Structure Example Link to heading

A typical K6 test project might look like this:

k6-load-tests/
├── tests/
│   ├── homepage.test.js
│   └── login.test.js
├── data/
│   └── users.csv
├── utils/
│   └── auth.js
└── k6.config.js

👨‍💻 Sample Advanced Script Link to heading

Login Simulation with Data Link to heading

data/users.csv

username,password
testuser1,pass1
testuser2,pass2

tests/login.test.js

import http from 'k6/http';
import { check, sleep } from 'k6';
import { SharedArray } from 'k6/data';

const users = new SharedArray('users', function () {
  return open('../data/users.csv').split('\n').slice(1).map(row => {
    const [username, password] = row.split(',');
    return { username, password };
  });
});

export const options = {
  vus: 5,
  duration: '20s',
};

export default function () {
  const user = users[Math.floor(Math.random() * users.length)];

  const payload = JSON.stringify({
    username: user.username,
    password: user.password,
  });

  const headers = { 'Content-Type': 'application/json' };

  const res = http.post('https://test-api.k6.io/auth/token/', payload, { headers });

  check(res, {
    'login success': (r) => r.status === 200,
  });

  sleep(1);
}

🧪 Test Types Link to heading

• Smoke Test: Run with 1–2 users to validate script
• Load Test: Simulate normal traffic
• Stress Test: Increase load until the system fails
• Spike Test: Sudden increase in users
• Soak Test: Long-duration test

🔗 Integration with CI/CD Link to heading

K6 can be easily integrated with tools like GitHub Actions:

jobs:
  load-test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2
      - name: Install k6
        run: sudo apt install k6 -y
      - name: Run Load Test
        run: k6 run tests/homepage.test.js

📈 Viewing Results Link to heading

• CLI metrics summary
• JSON or CSV output: k6 run --out json=output.json script.js
• Use k6 Cloud for dashboard

📚 Resources Link to heading

• Official Docs
• GitHub Repo
• Awesome k6

🎯 Conclusion Link to heading

K6 provides a fast, powerful, and developer-friendly way to ensure your system’s performance and resilience. With JavaScript scripting and seamless integrations, it becomes a must-have tool in your performance testing toolkit.

Happy Testing! 🚀